DIYmalls 4x4 Keypad 16 Keys Matrix Array Membrane Switch 8pin Keyboard Module for Arduino UNO R3 Pack of 5

Specification: Circuit Rating: DC 35V, 100mA, 1W Contact resistance: 10- 500? (Varies according to lead lengths and material used) Insulation resistance: 100M? 100V Dielectric Strength: 250VRms (50 ~ 60Hz 1min) Electric shock jitter: <5ms Life span: over 1 million times Key Operating Force: 150-200N Rebound time: 1 ms Operating pressure: Touch feeling: 170 ~ 397g (6 ~ 14oz) Switch travel: touch-type: 0.6 ~ 1.5mm Environment: Operating temperature: -40 to 80 Temperature: from 40,90% to 95%, 240 hours Vibration: 20G, max. (10 - 200Hz, Mil-SLD-202 M204.Condition B) How keypad works & How to scan them? The working principle is very simple. Pressing a button shorts one of row lines to one of column lines, allowing current to flow between them. A microcontroller can scan these lines for a button-pressed state. To do this, it follows steps below. 1.Microcontroller sets all column and row lines to input. 2.Then, it picks a row and sets it HIGH. 3.After that, it checks column lines one at a time. 4.If column connection stays LOW, button on the row has not been pressed. 5.If it goes HIGH, microcontroller knows which row was set HIGH, and which column was detected HIGH when checked. 6.Finally, it knows which button was pressed that corresponds to detected row & column. Note: 1. You can connect your keypad to any pins you would like. Be careful not to use serial pins (0 and 1) if you are using them for communication. 2. If key presses seem to take a long time to show up then you are probably using long delay()’s in your code. The same thing happens if you use too many small delay()s like delay(10). 3. Make sure you understand pin mappings and have keypad wired up to match. If you wired pins wrongly (and already soldered them in) then you may be able to fix it by redefining pins and/or keymap to make your keypad work